1. Field of the Invention
The present invention relates to an improvement of an outboard motor comprising a swivel case axially and steerably supporting a propulsion unit, a pair of left and right stern brackets disposed on left and right sides of the swivel case and supporting the swivel case in a vertically tiltable manner via a tilt shaft, and an upper pivot shaft and a lower pivot shaft that are parallel to the tilt shaft and are provided in the swivel case and the left and right stern brackets respectively, upper and lower end portions of an extendable part of a tilt system being mounted on the upper and lower pivot shafts.
2. Description of the Related Art
When a tilt system is mounted in a conventional outboard motor, as disclosed in, for example, Japanese Patent Application Laid-open No. 4-5190, one mounting part is provided on a central part of each of upper and lower pivot shafts. In the case of both a gas-assist type tilt system and a power type tilt system, upper and lower end portions thereof are mounted on the corresponding mounting parts provided on each of the upper and lower pivot shafts at central positions between left and right stern brackets.
In general, the gas-assist type tilt system employs an accumulator tank provided so as to be connected to one side of an assist cylinder and having a comparatively small diameter in the same way as the assist cylinder, whereas the power type tilt system employs a hydraulic pump and an electric motor provided so as to be connected to one side of a hydraulically operated cylinder and having larger diameters than that of the hydraulically operated cylinder. Therefore, if the assist cylinder or the hydraulically operated cylinder is mounted on the mounting parts in the center of the upper and lower pivot shafts, then the accumulator tank or the hydraulic pump and the electric motor are offset leftward or rightward from the central position between the left and right stern brackets, and consequently the entire tilt system is offset from the central position between the two stern brackets, thus impairing the appearance of the outboard motor.
The present invention has been achieved in view of the above-mentioned circumstances, and it is an object thereof to provide an outboard motor wherein either a gas-assist type or a power type tilt system can be mounted with good balance between left and right stern brackets, thereby improving the appearance.
In order to accomplish the above object, a first aspect of the present invention provides an outboard motor that includes a swivel case axially and steerably supporting a propulsion unit, a pair of left and right stern brackets disposed on left and right sides of the swivel case and supporting the swivel case. In a vertically tiltable manner via a tilt shaft, and upper and lower pivot shafts that are parallel to the tilt shaft and are provided in the swivel case and the left and right stern brackets respectively, upper and lower end portions of an extendable part of a tilt system being mounted on the upper and lower pivot shafts, wherein the upper pivot shaft includes first and second mounting parts that are offset in mutually opposite left and right directions from a central position between the pair of stern brackets, the offset of the second mounting part is set smaller than the offset of the first mounting part, and the upper end portion of the extendable part of the tilt system is mounted selectively on one of the first and second mounting parts according to the type of tilt system.
The tilt system corresponds to a power type tilt system 16P and a gas-assist type tilt system 16G of an embodiment of the present invention which will be described later, and the extendable part of the tilt system corresponds to a hydraulically operated cylinder 30 and an assist cylinder 40.
In accordance with this first aspect, since the upper end portion of the extendable part of the tilt system is selectively mounted on one of the first and second mounting parts of the upper pivot shaft according to the type of tilt system, by adjusting the size of a space formed beneath the other mounting part which is not used and arranging in this space an auxiliary equipment of the tilt system according to the size of the space, the entirety of the tilt system irrespective of the type can be arranged in the central position between the left and right stern brackets, thus achieving a good appearance of the outboard motor and a good weight balance in the left and right directions.
Furthermore, in accordance with a second aspect of the present invention, in addition to the first aspect, there is provided an outboard motor wherein the tilt system is of a power type in which a hydraulic pump and an electric motor are connected to one side of a hydraulically operated cylinder, an upper end part of the hydraulically operated cylinder is mounted on the first mounting part, and the hydraulic pump and the electric motor are disposed on the second mounting part side.
In accordance with this second aspect, the entire power type tilt system can be arranged in the central position between the left and right stern brackets, thus achieving a good appearance of the outboard motor and a good weight balance in the left and right directions.
Moreover, in accordance with a third aspect of the present invention, in addition to the first aspect, there is provided an outboard motor wherein the tilt system is of a gas-assist type in which a cylindrical accumulator tank is connected to one side of an assist cylinder, an upper end part of the assist cylinder is mounted on the second mounting part, and the accumulator tank is disposed on the first mounting part side.
In accordance with this third aspect, the entire gas-assist type tilt system can be arranged in the central position between the left and right stern brackets, thus achieving a good appearance of the outboard motor and a good weight balance in the left and right directions.
Furthermore, in accordance with a fourth aspect of the present invention, in addition to the first aspect, there is provided an outboard motor wherein the pair of left and right stern brackets are provided with a plurality of sets of pairs of left and right adjustment holes arranged in the vertical direction, a stopper pin that determines the tilted down position of the propulsion unit by receiving a stopper surface formed on a front surface of the swivel case is inserted through and supported selectively in one pair of the plurality of sets of adjustment holes so as to adjust the tilted down position of the propulsion unit in a plurality of steps, the swivel case has a second stopper surface formed below the stopper surface, the stern brackets have formed thereon a stopper wall that defines the lowest tilted down position of the propulsion unit by receiving the second stopper surface when the stopper pin is detached from the adjustment holes, and these stern brackets are provided with retention holes that retain the stopper pin detached from the adjustment hole.
In accordance with this fourth aspect, the number of adjustment positions of the tilted down position of the propulsion unit can be increased by one step with a very simple structure in which the second stopper surface is formed on the swivel case below the stopper surface and the stopper walls are formed on the stern brackets, the stopper walls defining the lowest tilted down position of the propulsion unit by receiving the second stopper surface when the stopper pin is detached from the adjustment holes. As a result, since it is unnecessary to increase the number of pairs of adjustment holes, there is no need to enlarge portions of the stern brackets where adjustment holes are to be provided, nor decrease in the turning angle of the propulsion unit. Moreover, in the case where the stopper pin is not in use, it can be retained in the retention holes of the stern brackets, thereby preventing it from being lost.
Furthermore, in accordance with a fifth aspect of the present invention, in addition to the fourth aspect, there is provided an outboard motor wherein, when the second stopper surface is received by the stopper wall, the swivel case is held between the two stern brackets.
In accordance with this fifth aspect, when the propulsion unit is trimmed to the lowest tilted down position, the lateral load acting on the swivel case can be firmly supported by the left and right stern brackets.
Moreover, in accordance with a sixth aspect of the present invention, in addition to the fourth or fifth aspect, there is provided an outboard motor wherein, when the stopper pin is inserted into the adjustment holes or the retention holes, a retaining key is axially supported on one end part of the stopper pin so that the retaining key can pivot between a dropped down position in which the retaining key is coaxial with the stopper pin and can pass through the adjustment holes or the retention holes together with the stopper pin, and a raised position in which the retaining key abuts against an outer side surface of one of the stern brackets, and a spring is fitted to the other end part of the stopper pin, the spring being compressed against an outer side surface of the other stern bracket and biasing the stopper pin in a direction opposite to the retaining pin.
In accordance with this sixth aspect, fitting of the stopper pin into the adjustment holes and the retaining holes and detachment therefrom can be carried out simply, and when the stopper pin is fitted the raised position of the retaining key can be maintained by the resilient force of the spring and noise due to rattling can be prevented.
The above-mentioned object, other objects, characteristics, and advantages of the present invention will become apparent from an explanation of preferred embodiments, which will be described in detail below, by reference to the attached drawings.